Rapid thermal processing (RTP) systems play an important role in the production of modern semiconductor devices. An ongoing challenge in RTP systems (and other systems used to process semiconductor devices) is precise control of processing cycles, namely controlling the heating of the object (or objects) being processed in the RTP chamber. Such objects typically comprise wafers, but may further include other configurations (e.g. ribbons, panels, etc.).
An RTP system can include a heating system that comprises one or more devices, including, but not limited to, lamps or lasers. Typically, these devices direct radiant energy into the chamber during a processing cycle based on a control program. The control program comprises one or more parameters which are used to adjust the amount of power applied to the heating system.
For instance, in some systems, “closed-loop” control can be based on the temperature of a wafer being processed. The control program may receive data from one or more measurement devices that monitor the wafer temperature and adjust power settings of the heating system.
As another example, a wafer (or other object) may be processed under “open-loop” control wherein a predetermined set of control values are used to adjust the power settings of the heating system without regard to the wafer's status. For instance, in some systems, an instrumented wafer may be placed into a chamber that heats the wafer via a plurality of lamps. The lamp power settings over the course of the process may be controlled so that the wafer follows a desired temperature trajectory. The lamp power settings may be recorded and played back to control the heating of other wafers.
Ongoing developments in semiconductor structures, however, would be better supported in some instances by more precise temperature control during processing.